package org.checkerframework.javacutil;

import com.sun.source.tree.ClassTree;
import com.sun.source.util.JavacTask;
import com.sun.source.util.TaskEvent;
import com.sun.source.util.TaskListener;
import com.sun.source.util.TreePath;
import com.sun.source.util.Trees;
import com.sun.tools.javac.comp.CompileStates.CompileState;
import com.sun.tools.javac.main.JavaCompiler;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import java.util.HashSet;
import java.util.Set;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.lang.model.element.Name;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.ElementFilter;
import org.checkerframework.dataflow.qual.SideEffectFree;

/**
 * This class is an abstract annotation processor designed to be a convenient superclass for
 * concrete "type processors", processors that require the type information in the processed source.
 *
 * <p>Type processing occurs in one round after the tool (e.g. Java compiler) analyzes the source
 * (all sources taken as input to the tool and sources generated by other annotation processors).
 *
 * <p>The tool infrastructure will interact with classes extending this abstract class as follows.
 *
 * <p>1-3 are identical to the {@link Processor} life cycle. 4-5 are unique to {@code
 * AbstractTypeProcessor} subclasses.
 *
 * <ol>
 *   <li>If an existing {@code Processor} object is not being used, to create an instance of a
 *       processor the tool calls the no-arg constructor of the processor class.
 *   <li>Next, the tool calls the {@link #init init} method with an appropriate {@code
 *       ProcessingEnvironment}.
 *   <li>Afterwards, the tool calls {@link #getSupportedAnnotationTypes
 *       getSupportedAnnotationTypes}, {@link #getSupportedOptions getSupportedOptions}, and {@link
 *       #getSupportedSourceVersion getSupportedSourceVersion}. These methods are only called once
 *       per run, not on each round.
 *   <li>For each class containing a supported annotation, the tool calls {@link
 *       #typeProcess(TypeElement, TreePath) typeProcess} method on the {@code Processor}. The class
 *       is guaranteed to be type-checked Java code and all the tree type and symbol information is
 *       resolved.
 *   <li>Finally, the tool calls the {@link #typeProcessingOver typeProcessingOver} method on the
 *       {@code Processor}.
 * </ol>
 *
 * <p>The tool is permitted to ask type processors to process a class once it is analyzed before the
 * rest of classes are analyzed. The tool is also permitted to stop type processing immediately if
 * any errors are raised, without invoking {@link #typeProcessingOver}.
 *
 * <p>A subclass may override any of the methods in this class, as long as the general {@link
 * javax.annotation.processing.Processor Processor} contract is obeyed, with one notable exception.
 * {@link #process(Set, RoundEnvironment)} may not be overridden, as it is called during the
 * declaration annotation phase before classes are analyzed.
 */
public abstract class AbstractTypeProcessor extends AbstractProcessor {
  /**
   * The set of fully-qualified element names that should be type-checked. We store the names of the
   * elements, in order to prevent possible confusion between different Element instantiations.
   */
  private final Set<Name> elements = new HashSet<>();

  /**
   * Method {@link #typeProcessingStart()} must be invoked exactly once, before any invocation of
   * {@link #typeProcess(TypeElement, TreePath)}.
   */
  private boolean hasInvokedTypeProcessingStart = false;

  /**
   * Method {@link #typeProcessingOver} must be invoked exactly once, after the last invocation of
   * {@link #typeProcess(TypeElement, TreePath)}.
   */
  private boolean hasInvokedTypeProcessingOver = false;

  /** The TaskListener registered for completion of attribution. */
  private final AttributionTaskListener listener = new AttributionTaskListener();

  /** Constructor for subclasses to call. */
  protected AbstractTypeProcessor() {}

  /**
   * {@inheritDoc}
   *
   * <p>Register a TaskListener that will get called after FLOW.
   */
  @Override
  public synchronized void init(ProcessingEnvironment env) {
    super.init(env);
    JavacTask.instance(env).addTaskListener(listener);
    Context ctx = ((JavacProcessingEnvironment) processingEnv).getContext();
    JavaCompiler compiler = JavaCompiler.instance(ctx);
    compiler.shouldStopPolicyIfNoError =
        CompileState.max(compiler.shouldStopPolicyIfNoError, CompileState.FLOW);
    compiler.shouldStopPolicyIfError =
        CompileState.max(compiler.shouldStopPolicyIfError, CompileState.FLOW);
  }

  /**
   * The use of this method is obsolete in type processors. The method is called during declaration
   * annotation processing phase only. It registers the names of elements to process.
   */
  @Override
  public final boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
    for (TypeElement elem : ElementFilter.typesIn(roundEnv.getRootElements())) {
      elements.add(elem.getQualifiedName());
    }
    return false;
  }

  /**
   * A method to be called once before the first call to typeProcess.
   *
   * <p>Subclasses may override this method to do any initialization work.
   */
  public void typeProcessingStart() {}

  /**
   * Processes a fully-analyzed class that contains a supported annotation (see {@link
   * #getSupportedAnnotationTypes()}).
   *
   * <p>The passed class is always valid type-checked Java code.
   *
   * @param element element of the analyzed class
   * @param tree the tree path to the element, with the leaf being a {@link ClassTree}
   */
  public abstract void typeProcess(TypeElement element, TreePath tree);

  /**
   * A method to be called once all the classes are processed.
   *
   * <p>Subclasses may override this method to do any aggregate analysis (e.g. generate report,
   * persistence) or resource deallocation.
   *
   * <p>Method {@link #getCompilerLog()} can be used to access the number of compiler errors.
   */
  public void typeProcessingOver() {}

  /**
   * Returns the compiler log, which contains errors and warnings.
   *
   * @return the compiler log, which contains errors and warnings
   */
  @SideEffectFree
  public Log getCompilerLog() {
    return Log.instance(((JavacProcessingEnvironment) processingEnv).getContext());
  }

  /** A task listener that invokes the processor whenever a class is fully analyzed. */
  private final class AttributionTaskListener implements TaskListener {

    @Override
    public void finished(TaskEvent e) {
      if (e.getKind() != TaskEvent.Kind.ANALYZE) {
        return;
      }

      if (!hasInvokedTypeProcessingStart) {
        typeProcessingStart();
        hasInvokedTypeProcessingStart = true;
      }

      if (!hasInvokedTypeProcessingOver && elements.isEmpty()) {
        typeProcessingOver();
        hasInvokedTypeProcessingOver = true;
      }

      if (e.getTypeElement() == null) {
        throw new BugInCF("event task without a type element");
      }
      if (e.getCompilationUnit() == null) {
        throw new BugInCF("event task without compilation unit");
      }

      if (!elements.remove(e.getTypeElement().getQualifiedName())) {
        return;
      }

      TypeElement elem = e.getTypeElement();
      TreePath p = Trees.instance(processingEnv).getPath(elem);

      typeProcess(elem, p);

      if (!hasInvokedTypeProcessingOver && elements.isEmpty()) {
        typeProcessingOver();
        hasInvokedTypeProcessingOver = true;
      }
    }

    @Override
    public void started(TaskEvent e) {}
  }
}
